Once a photograph of the Earth, taken from outside, is available, we shall, in an emotional sense, acquire an additional dimension... Once let the sheer isolation of the Earth become plain to every man, whatever his nationality or creed, and a new idea as powerful as any in history will be let loose.
(1948)

Well, we now have such a photograph... Has any new idea been let loose? It certainly has. You will have noticed how suddenly everybody has become seriously concerned to protect the natural environment... It seems to me more than a coincidence that this awareness should have happened at exactly the moment man took his first step into space.